Automatic musical performance method and apparatus for a keyed instrument

ABSTRACT

As the key elements and other elements of an electronic organ are manually played to perform a musical composition, an electronic circuit generates groups of parallel digital signals which continuously represent the positions of the elements at sequential points in time. The parallel signals are converted to a serial signal varying with time, and the serial signal is recorded on tape. For automatic operation of the organ, the recorded signal is reproduced and reconverted to the original parallel signal groups which are applied to the organ to operate it so that it automatically plays the same composition that was originally played manually.

United States Patent 1191 1111 3,868,882 Fukui et a1. 1 Mar. 4, 1975 [54] AUTOMATIC MUSICAL PERFORMANCE 3,610,799 l0/1971 Watson 8411.01 ET D AND APPARATUS FOR A KEYED 3,634,596 1/1972 Rupert 84/128 m gg 3,647,929 3/1972 Milde, Jr 84/101 3,696,201 10/1972 Arsem et al. 84/101 [75] Inventors: Tutomu Fukui; Tsutomu Suzuqui, 3,771,406 11/1973 heelwright-... /464 both of Tokyo, Japan 3,781,452 12/1973 Vauclam 84/128 3,789,719 2/1974 Matllet 84/115 1 Assignoe: Pioneer Electronic C p a o 3,800,060 3/1974 Hallman, Jr. 84/101 x Tokyo, Japan 3,829,597 8/1974 Peterson et a1. 84/1.03 [22] Filed:' Nov. 19, 1973 Primary ExammerR1chard B. W11k1ns0n 1 1 pp N911 417,331 Assistant E.\'aminer-Stanley J. Witkowski Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, [30] Foreign Application Priority Data Zmn Macpeak Nov. 17, 1972 Japan 47-115439 [57] ABSTRACT [52] U.S. Cl 84/462, 84/103, 84/128, AS the key elements and other elements of an elec 84/] 15 tronic organ are manually played to perform a musical 51 l llt. Cl..... Gl0g 3/04 Composition an electronic circuit generates groups of held of Search 84/l.0l-l.03, parallel digital Signals which continuously represent 84/138 1151461 462 the positions of the elements at sequential points in time. The parallel signals are converted to a serial sig- [561 References cued nal varying with time, and the serial signal is recorded UNITED S A S ATENTS on tape. For automatic operation of the organ, the re- 2 714,633 8/1955 Fine 84/1.02 X Corded signal is reproduced and reconvened to the 2 843.676 7/1958 Halliday 84/D1G. 29 original parallel signal groups which are applied to the 3 277,245 10/1966 Sponga 84/462 X organ to operate it so that it automatically plays the 3,467,758 9/1969 Martin 84/102 a e c mposition that was originally played manually 3,539,701 11/1970 Milde 84/128 3,604,299 9/1971 Englund 84/103 9 Claims, 8 Drawing Figures +5v KBU KBL FP EP EFL TOL VR tP EP EFL TOL KBL KBU SW1 SR VCO l o sp P/S P/S P/S LA LA LA SPG PC PATENTEU MAR 75 sum 1 a; 4

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an automatic musical performance method and apparatus for a keyed instrument, and more particularly to an automatic musical performance method and apparatus for an electronic organ and other kinds of keyed instruments in which perfect automatic muscial performance may be carried out by means of recording and reproducing operations of key boards, tone levers, effect levers and the like of the electronic organ in digital manner.

2 Description of Prior Art A magnetic recording tape or a disk on which music is recorded as played has been used for appreciation of organ music or for teaching organ lessons. In this method, however, it is impossible to rearrange a previously recorded music composition later; namely, it is impossible to change playing speed without changing the musical interval, to transpose without changing playing speed, or to change the quality of a sound, as one pleases.

Also well known is an automatic musical performance instrument which makes use of the technique of punching a paper tape in positions corresponding to the keys to be played, and then automatically playing the piano under the control of the punched paper tape. However, this kind of autopiano has not only the disadvantage of being large-sized, but also the disadvantage of complexity for recording and playing back a control signal for automatic performance.

SUMMARY or THE INVENTION This invention overcomes the above-mentioned problems by making it possible to provide an automatic musical performance of a keyed instrument by a quite new method.

The primary object of the present invention is to provide an automatic musical performance method and apparatus for a keyed instrument and which are characterized by converting into a serial pulse line signal changing with time a group of parallel signals formed by ON-OFF signals produced by operating keys and the like of the keyed instrument, recording the converted serial pulse line signal, reproducing the recorded serial pulse line signal for the automatic musical performance, reeonverting the reproduced serial pulse line signal into a group oforiginal parallel signals, and controlling the keyed instrument by the re'coverted parallel signals, thereby automatically playing music on a keyed instrument.

Now, one embodiment of an automatic music performance apparatus in accordance with the present invention method will be exaplained in detail in conjunction with the accompanying drawings. A one-gate type organ with indirect keying is used in this embodiment, but a direct keying type organ may be used with the present invention by adding a few circuits or devices, or by mechanically operating keys.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the whole construction of an automatic music performance apparatus in accordance with the present invention.

FIG. 2 is a parallel view of an upper key board and its attached device.

FIG. 3 is a partial view of a parallel serial converter.

FIG. 4 is an explanation diagram of an expression pedal device.

FIGS. 5A and 5B are a block diagram of a decoder circuit and a diagram showing signal waveforms at some points, respectively.

FIG. 6 is a partial view of a serial parallel converter.

FIG. 7 is a diagram showing a clock-pulse signal, a synchronizing pulse signal and keying signals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. I is a block diagram showing the entire construction of the present apparatus including the following elements: upper key board KBU; foot pedal FP; effect lever EFL; parallel-to-serial converting circuit P/S; non-return-to-zero writing amplifier N/W; lower key board KBL; expression pedal EP; tone lever TOL; magnetic recording heads HRl-HR4; clock-pulse generating circuit VCO; synchronizing pulse generating circuit SPG; phase comparison circuit PC; play-back heads HPl-HP4; decoder circuit DEC; delay circuit DE; bitdelay circuit BD; serial-in, parallel-out converting circuit S/P; and latching circuit LA.

Next, main elements of the above-mentioned construction elements will be explained in detail.

FIG. 2 represents a portion of keys in the upper key board KBU and circuits attached to them. Natural and chromatic keys K1 to K8 of the upper keyboard KBU have switches k1 to 8 turned on and off by touching them in each corresponding place, respectively. Byoperation of theseswitches'kl to k8, tone generators, not shown, of the electric organ are controlled to emit a sound in accordance with the keys touched, and control signals to be recorded for automatic musical performance are generated. P-OUT 1 to P-OUT 8 are output lines coupled to parallel-to-serial converter P/S. Further, the switches kl to k8 are respectively connected in parallel with series circuitsof field effect transistors F1 to F8 and electro-luminous diodes E1 to E8. These field effect transistors turn on or off, in automatic performance, by receiving control signals from the latching circuit LA through input lines P-INl to P- IN8, whereby the electro-luminous diodes E1 to E8 buried in each of keys (or other indicating means corresponding with the keyboards) light to indicate playing-back keys, and the electric organ is controlled for automatic performance just as the switches kl to k8 turn on and off. The explanations, for the lower keyboard KBL, the foot pedals FP, the effect levers EFL and the tone levers TOL and so on, will be omitted because these basically have the same constructions as the upper keyboard KBU.

FIG. 3 represents one kind of eight-bit parallel-in, serial-out converter. A parallel-to-serial converter having the required number of bits in multiples of eight may be constructed by connecting the output line S-OUT of one to the input line S-IN of another. This parallel-to-serial converter P/S is a circuit for converting a group of parallel ON-OFF signals appearing in parallel by manipulating each keyboard KBU, KBL and FP and/or each lever EFL and TOL into a serial pulse line signal changing with the passing of time (in this embodiment, an eight-bit parallel-in, serial-out shift register is used). The parallel-to-serial converter used in practice has as many bits as the switches contained in all the control key means, such as keyboards, levers and pedals. In this embodiment, 61 -bit parallel-toserial converters are used for each of the upper and lower keyboards KBU and KBL, respectively. As to the others, another parallel-to-serial converter having 61 bits in total, namely 4 bits for the expression pedal, 13 bits for the foot pedals and 44 bits for the tone levers TOL and the effect levers EFL, is used.

FIG. 4 is a schematic diagram of the expression pedal EP. A shutter M is operated by an expression pedal (not shown), which shutter M slides in accordance with pressing of the pedal between light sources and photosensors PS. The shutter M has in it slits S1 to S4 cut through in accordance with the illustrated 16-step gray code corresponding with the decimal numbers zero to 15 Each of photo-transistors P1 to P4 of the photosensor PS detects the light passing through the slits S and encodes the pressing depth of the expression pedal as a volume control signal. This encoded 4 -bit volume control signal is applied to the parallel-to-serial converter P/S through output linesP-OUTI to P-OUT4, converted in the same manner as the keyboard signals into a serial pulse line signal changing with the passing of time, and then recorded.

On the one hand, the volume control signal is applied to a diode matrix circuit MX through OR circuits, whereby the matrix circuit MX produces an output signal at a corresponding one of output terminals OUTO to OUTIS. A conventional volume control circuit (not shown) is controlled by the output signal. For automatic performance, volume control signals coming from a latching circuit LA to input lines P-IN are applied to the diode matrix circuit MX to control the volume control circuit just as in manual performance.

FIGS. 5A and 58 represent a decoder circuit DEC and waveforms at some points of the circuit, respectively. Each decoder circuit DEC amplifies signals reproduced by means of the corresponding play-back head HPl to HP4 and reforms them to the original recording signal waveforms. The circuit is composed of a sensing amplifier SA, diodes D1 to D3, an operational amplifier A, a Schmitt trigger circuit ST, a T-type flip flop circuit TFF, an inverter l and so on. When'magnetic signals on a magnetic tape as shown at a of FIG. B are picked up by means of the play-back heads, the output signals become pulse signals as shown at b. When such pulse signals come to the decoder circuit DEC, the signals are amplified to a sufficient level by the sensing amplifier SA, separated according to polarity by diodes D1 and D2, and applied to the inputs of the operational amplifier 0A. At the time, negative pulses adding through-the diode D1 are applied to the inverting input terminal, and positive pulses adding through the Diode D2 are applied to the noninverting input terminal; therefore, the output signals from the operational amplifier 0A are a full-wave rectified version of the output signals of the sensing amplifier SA. The output waveform of amplifier 0A is shown at line The waveform of the output signal of the operational amplifier 0A is shaped by the Schmitt trigger circuit ST into a square pulse line signal shown in d, and then is applied to the T-type flip flop TFF. Since the output of this T-type flip flop TFF functions to switch its output on each positive going edge of the input signal, the input signal d is converted into a signal as shown in e and this becomes an output signal of the decoder circuit DEC.

The decoder circuit described so far is subject to producing an improperly inverted output signal relative to the required signal when an input pulse is not reproduced on account of dropping-out of a magnetic tape and the like. Consequently, a feed-back circuit composed of an inverter I and a diode D3 is so added as to minimize error caused by such a condition. If, for example, the pulse marked by x in FIG. 5B is not played back, the errors in the output signal are kept to a few because the output signal of the decoder circuit DEC becomes as shown in e. Namely, when the output signal level of the T-type flip flop TFF is positive the output signal of the inverter I goes to the zero level to render diode D3 conducting, and thus the next positive going pulse coming from the sensing amplifier SAdoes not reach the operational amplifier OA. If the decoder circuit DEC is further improved so that a negative going pulse also does not add to the operational amplifier OA when the output of the flip flop TFF is at the zero level, the error caused by the dropping-out of the tape is further minimized. In this decoder, the diodes D1 and D2 and the operational amplifier 0A are used for making the polarities of the output signal of the sensing amplifier SA uniform, but this function may be performed by other means, such as a full wave rectification circuit. Even in this case, of course, a feedback circuit, such as described above, is necessary for rectifying an input signal, subject to drop out error, in the proper order of positive-negative-positive-negative. The inverter I used in the feedback circuit is used primarily to isolate the input and output of amplifier CA from each other; therefore, the inverter I is not necessary if the Q output terminal of the flip flop TF F is used for the feedback circuit.

FIG. 6'shows a serial-to-parallel converter S/P. This circuit S/P converts into a group of original parallel pulses, the serial pulse line signal changing with the passing of time and arriving at input lines S-IN via a decoder circuit DEC and a bit-delay circuit BD. In this embodiment, a conventional 61 -bit serial-in, parallelout shift-register is used as a parallel-to-serial converter.

Next, the operation of the automatic musical performance apparatus will be explained. First, the explanation will begin with the recording of a keying pattern or control signals. To place the apparatus in the state for recording control signals, the movable contact of switch SW1 in FIG. 1 is placed in engagement with the fixed contact SR. Therefore, a clock-pulse generating circuit VCO, the frequency of which is voltagecontrolled, is controlled by a fixed voltage to generate a clock-pulse signal of 3000Hz as shown on line a of FIG. 7. A synchronizing-pulse generating circuit SPG counts the clock-pulses to generate as a synchronizing pulse signal one pulse every 62 bits, as shown on line b of FIG. 7.

Consequently, when an organist plays or operates the upper keyboard KBU, the lower keyboard KBL, the foot pedals FP, the expression pedal EP, the effect lever EFL, and the tone levers TOL to produce music, the switches corresponding to each key and each lever and the like turn on and off in response to the manual playing or operations of the organist, and the output signals obtained from these switches fed to the corresponding parallel-to-serial converters P/S. For example, when keys K1 and K4 of the upper keyboard KBU are touched at the same time, switches kl and k4 close respectively, and thereby DC current or signals are fed to the corresponding parallel-to-serial converter P/S through output lines P-OUTl and P-OUT4. The signals corresponding to keys K1 to K4 fed to the parallel-toserial converter P/S are applied through input lines INl and [N4 to the shift register shown in FIG. 3. These key signals are preset at once in corresponding shift register flip flops FF by a synchronizing pulse having a pulse width of one bit and which occurs about every oneforty-eighth second. The preset signals are then shifted out of the shift register in order by incoming clockpulses, and thus are converted to a serial pulse line signal as shown in line (c) of FIG. 7. Namely, an input signal group applied in parallel to the parallel-to-serial converter P/S is converted into a serial pulse line signal changing with the passing of time, and then is applied to its corresponding writing amplifier NW. The serial pulse line signal applied to the writing amplifier NW is changed here from an unbalanced signal mode to a balanced signal mode, and is recorded in NRZ (No Return to Zero) form by means of the recording head HRl on a first track of the magnetic recording tape.

The circuit operation as mentioned above may be applied to the other keyboard KBL, the foot pedal PP and all the levers EFL and TOL in the same manner as to the upper keyboard KBU. As for the expression pedal EP, there is no difference from the upper keyboard KBU except for encoding a pressed depth of the expression pedal into a four-bit pulse signals The signal from the lower keyboard KBL is recorded on a second track, the other signals on a third track, and the synchronizing pulse signal on the fourth track, respectively.

Explained below is an example of an automatic musical performance carried out in accordance with the signals recorded by the method described above. Four channels of the pulse line signals are picked up by means of the play-back heads HPl to HP4 corresponding with each recorded track. Each channel is applied to a corresponding decoder DEC where the signals are amplified, recoverted to the unbalanced signal mode, and are decoded to the original recording signal by the diodes D1 and D2, the operational amplifier A, the Schmitt trigger circuit ST and the flip flop TFF, all as described above in connection with FIG. 5.

The decoded signals of the first to third-tracks, i.e-., the signals obtained by the operation of every key, lever and pedal, are applied to the bit-delay circuits BD to be delayed by one bit therein. On the one hand, the decoded fourth-track synchronizing pulse signal is delayed by the delay circuit DE which is capable of delaying it for any time during a one-bit time period by the time necessary for compensating for the time lag between the synchronizing pulse signal and other operation signals, which time lag occurs in the process of recording and reproducing.

The synchronizing pulse signal thus reproduced and recoverted enters the phase comparing circuit PC consisting of a phase-locked loop circuit together with the clock-pulse generating circuit VCO, and is compared in phase with the output signal of the synchronizingpulse generating circuit SPG. The result of the phase comparison is fed back to the clock-pulse generating circuit VCO through a switch SW1 shown in FIG. 1. Thcreforc.'the pulsc signals having the most appropriate phase relationship between them are always applied from both the clock-pulse generating circuit VCO and the synchronizing pulse generating circuit SPG to any other circuits.

Each serial pulse line signal going out of every bitdelay circuit BD enters the shift register of the shift register of the serial-to-parallel converter S/P (FIG. 6) via the input line S-IN thereofin proper order and synchronized with the clock-pulse signal added to it at the same time. Consequently, the same signal appears on the output line Pn-OUT of the nth flip flop FF of the shift register one clock-pulse bit later than it appears on (nl)th output line P(n1)-OUT. Namely, the signals are shifted bit by bit through every output line of the shift register to accomplish serial-to-parallel conversion. Assuming that time stopped at some bit of the clock-pulse signal, then serial pulse line output signals at that time will correspond to the serial pulse line signal already converted into a parallel signal pattern. Therefore, in practice a parallel signal group, changing its contents with the frequency of the clock-pulse signal, appears on the output lines P-OUT of the flip flops FF, and it is applied to the latching circuit LA The signal group applied to the latching circuit LA as a parallel pulse signal group changing with the frequency of the clock-pulse signal is stored in the latching circuit LA when the synchronizing pulse signal having a pulse width of one-bit adds to it. Namely, the latching circuit stores a pattern of the parallel signal group coming to the latching circuit LA at the very time when the synchronizing pulse signal is about to add to it, and then holds it as the output of the latching circuit through about 1/48 second until the next synchronizing pulse signal comes, regardless of the presence or absence of input signals.

Every output signal of the latching circuit obtained like this is applied to a gate circuit corresponding to every key, every lever or the like, for example a gate electrode of the every field effect transistor as shown in FIG. 2 in order to turn it on and off, whereby the electroluminous diode lights to indicate a playing key, and the electric organ is automatically controlled just as an organist manually plays the electric organ. The electric organ is perfectly controlled for playing organ music on the basis of the chain of operations explained above.

In this embodiment, the present invention is applied to an electric organ. However, the present invention may be applied to other different kinds of keyed instruments, for example an electronic piano or an ordinary piano. When the present invention is applied to an ordinary piano, the object is achieved by automatically controlling the keys by operating an electro-magnetic plunger with the output signal of the latching circuit, but it is necessary to add another device for reconstruction of the strength and weakness of touching force applied to the keys.

The method and apparatus of the present invention is described above have achieved the foregoing objects perfectly, and further have the following features or merits.

First, since the present invention converts into a serial pulse line signal a parallel signal group formed by ON-OFF signals produced by operating keys and then records and reproduces the converted serial pulse line signal, the recording and the reproducing of the signals not only may be carried out by the use of an ordinary tape recorder of simple construction and without making use of a digital tape recorder having many recording tracks, but in addition the tone quality and musical interval is never modified by wow or flutter of the tape.

Second, the invention permits an organ to be played by hand simultaneously with an automatic music performance by the organ; therefore, the invention permits a player to play only the melody of a musical composition to the accompaniment of the music being automatically played by the apparatus.

Third, since indicating means are provided for indicating the keys being played, one can listen to the music while observing the variation of the keying pattern. Further, it is preferable during the teaching of an organ lesson that a luminous indicating element be mounted in every key.

Fourth, one is capable of listening to a recorded music transposed at ones option in automatic music performance because one is able to transpose a recorded music at ones option only to delay keying signals or a synchroning pulse signal. Yet, since signals of low-pitched sound positions are shifted to high-pitched sound positions if all the bits being between two adjacent synchronizing pulses are used for keying signals, it is necessary to establish a number of total bits between two adjacent synchronizing pulses in a total number of a number of keys and a number of delay bits necessary for transposition.

Further, one is able to change musical performance speed without modifying a musical interval.

We claim:

1. A reproducing apparatus for use in.an automatic musical performance apparatus for a keyed instrument, said reproducing apparatus accepting a prerecorded tape having recorded thereon a serial pulse line signal changing with time representing the operation of the keys of the keyed instrument and a synchronizing signal, said reproducing apparatus comprising:

a. reproducing means for reproducing the previously recorded synchronizing signal andthe previously recorded serial pulse line signal representative of the key operation for producing the musical composition;

b. phase-locked loop means receiving said reproduced synchronizing signal for generating a clock pulse in accordance with the synchronizing signal;

c. serial-to-parallel converting circuit means coupled to receive said clock pulse for converting the serial pulse line signal into a parallel signal group;

d. latching circuit means coupled to said converting circuit means for storing the value ofa signal group until the occurrence of the next synchronizing signal; and

e. means coupling said latching circuit means to the music producing elements of said instrument.

2. A method of automatically playing a musical composition on a keyed instrument which comprises:

a. generating groups of parallel digital signals by operating the keys of the instrument in accordance with the musical composition, each signal being representative of the position of a corresponding key;

b. generating a first synchronizing signal;

0. converting the groups of parallel signals into a serial pulse line signal in synchronism with the first synchronizing signal;

d. recording the converted serial pulse line signal and the first synchronizing signal;

e. reproducing the recorded serial pulse line signal and the first synchronizing signal, for the automatic musical performance;

f. generating a second synchronizing signal;

g. comparing the reproduced first synchronizing signal with the generated second synchronizing signal and correcting the frequency of the second synchronizing signal in accordance with any deviation with said reproduced first synchronizing signal;

h. reconverting the reproduced serial pulse line signal into the original groups of parallel signals in synchronism with the second synchronizing signahand i. controlling the keyed instrument by the reconverted parallel signals, thereby automatically performing a music for a keyed instrument.

3. The method as defined in claim 2 wherein said generating step further comprises encoding at least one group of said parallel digital signals in accordance with the Gray code.

4. Control signal recording apparatus for use in an automatic musical performance apparatus for a keyed instrument comprising:

a. a clock-pulse generating circuit; v

b. a synchronizing-signal generating circuit;

c. a parallel-to-serial converting circuit means coupled to said clock pulse and synchronizing signal I generating circuits for converting into a serial pulse line signal changing with time digital signal groups sequentially generated by operation of the keys of the keyed instrument;

d. recording means coupled to said converting circuit means for recording the serial pulse line signal and the synchronizing signal;

e. reproducingmeans for reproducing the previously recorded synchronizing signal and the previously recorded serial pulse line signal representative of the key operation for producing the musical composition;

f. phase-locked loop means including said clockpulse generating circuit receiving said reproduced synchornizing signal for generating a clock pulse in accordance with the synchronizing signal;

g. serial-to-parallel converting circuit means coupled to said clock pulse generating circuit for converting the serial pulse line signal into the original parallel signal groups;

h. latching circuit means coupled to said converting circuit means for storing the value of a signal group until the occurrence of the next synchronizing signal; and

i. means coupling said latching circuit means to the music producing elements of said instrument.

5. Apparatus as defined in claim 4 further comprising indicating means mounted on the instrument keys and coupled to said latching circuit means for indicating operated keys.

6. The apparatus as defined in claim 4 further comprising decoder circuit means for decoding each of the reproduced signals into a corresponding square wave signal, said decoder circuit means comprising trigger means responsive to each reproduced signal for producing corresponding square pulses of uniform amplitude, and flip-flop circuit means responsive to said pulses for producing a square wave signal whose successive positive and negative going transitions correspond respectively to successive ones of said square pulses.

7. The apparatus as defined in claim 6 wherein said reproduced signals are alternately positive and negative with respect to a reference and said decoder circuit means further comprises full wave rectifier means preceding said trigger means for converting the reproduced signals to a uniform polarity.

8. The apparatus as defined in claim 7 wherein said decoder means further comprises feedback means connected between said flip-flop circuit and said full wave rectifier means for minimizing drop-out error in reproducing the recorded pulse signal.

9. The apparatus as defined in claim 4, wherein said between said synchronizing pulses. 

1. A reproducing apparatus for use in an automatic musical performance apparatus for a keyed instrument, said reproducing apparatus accepting a prerecorded tape having recorded thereon a serial pulse line signal changing with time representing the operation of the keys of the keyed instrument and a synchronizing signal, said reproducing apparatus comprising: a. reproducing means for reproducing the previously recorded synchronizing signal and the previously recorded serial pulse line signal representative of the key operation for producing the musical composition; b. phase-locked loop means receiving said reproduced synchronizing signal for generating a clock pulse in accordance with the synchronizing signal; c. serial-to-parallel converting circuit means coupled to receive said clock pulse for converting the serial pulse line signal into a parallel signal group; d. latching circuit means coupled to said converting circuit means for storing the value of a signal group until the occurrence of the next synchronizing signal; and e. means coupling said latching circuit means to the music producing elements of said instrument.
 2. A method of automatically playing a musical composition on a keyed instrument which comprises: a. generating groups of parallel digital signals by operating the keys of the instrument in accordance with the musical composition, each signal being representative of the position of a corresponding key; b. generating a first synchronizing signal; c. converting the groups of parallel signals into a serial pulse line signal in synchronism with the first synchronizing signal; d. recording the converted serial pulse line signal and the first synchronizing signal; e. reproducing the recorded serial pulse line signal and the first synchronizing signal, for the automatic musical performance; f. generating a second synchronizing signal; g. comparing the reproduced first synchronizing signal with the generated second synchronizing signal and correcting the frequency of the second synchronizing signal in accordance with any deviation with said reproduced first synchronizing signal; h. reconverting the reproduced serial pulse line signal into the original groups of parallel signals in synchronism with the second synchronizing signal; and i. controlling the keyed instrument by the reconverted parallel signals, thereby automatically performing a music for a keyed instrument.
 3. The method as defined in claim 2 wherein said generating step further comprises encoding at least one group of said parallel digital signals in accordance with the Gray code.
 4. Control signal recording apparatus for use in an automatic musical performance apparatus for a keyed instrument comprising: a. a clock-pulse generating circuit; b. a synchronizing-signal generating circuit; c. a parallel-to-serial converting circuit means coupled to said clock pulse and synchronizing signal generating circuits for converting into a serial pulse line signal changing with time digital signal groups sequentially generated by operation of the keys of the keyed instrument; d. recording means coupled to said converting circuit means for recording the serial pulse line signal and the synchronizing signal; e. reproducing means for reproducing the previously recorded synchronizing signal and the previously recorded serial pulse line signal representative of the key operation for producing the musical composition; f. phase-locked loop means including said clock-pulse generating circuit receiving said reproduced synchornizing signal for generating a clock pulse in accordance with the synchronizing signal; g. serial-to-parallel converting circuit means coupled to said clock pulse generating circuit for converting the serial pulse line sigNal into the original parallel signal groups; h. latching circuit means coupled to said converting circuit means for storing the value of a signal group until the occurrence of the next synchronizing signal; and i. means coupling said latching circuit means to the music producing elements of said instrument.
 5. Apparatus as defined in claim 4 further comprising indicating means mounted on the instrument keys and coupled to said latching circuit means for indicating operated keys.
 6. The apparatus as defined in claim 4 further comprising decoder circuit means for decoding each of the reproduced signals into a corresponding square wave signal, said decoder circuit means comprising trigger means responsive to each reproduced signal for producing corresponding square pulses of uniform amplitude, and flip-flop circuit means responsive to said pulses for producing a square wave signal whose successive positive and negative going transitions correspond respectively to successive ones of said square pulses.
 7. The apparatus as defined in claim 6 wherein said reproduced signals are alternately positive and negative with respect to a reference and said decoder circuit means further comprises full wave rectifier means preceding said trigger means for converting the reproduced signals to a uniform polarity.
 8. The apparatus as defined in claim 7 wherein said decoder means further comprises feedback means connected between said flip-flop circuit and said full wave rectifier means for minimizing drop-out error in reproducing the recorded pulse signal.
 9. The apparatus as defined in claim 4, wherein said phase-locked loop means comprises: a. said clock-pulse generating circuit including a voltage controlled oscillator for generating said clock pulse at a frequency determined by a control voltage; b. a synchronizing pulse generator connected to receive said clock pulse and generate a synchronizing pulse; and c. phase comparator means receiving the reproduced and generated synchronizing pulses for producing said control voltage as a function of the deviation between said synchronizing pulses. 